1998 Honda Accord Clutch rleases

When sitting at stop with brake and clutch pedal pressed, such as at stop sign, the clutch will slowly engage after a 15-20 second period even though it is still fully pressed to the floor. The same if you are in neutral. After the same amount of time you can't get car into gear unless you release clutch and press again to re-engage. The clutch fluid level is normal and there are no apparent leaks that would cause the loss in clutch pressure.